/*
 * Copyright (c) 2015, Nils Braden
 *
 * This file is part of ttrss-reader-fork. This program is free software; you
 * can redistribute it and/or modify it under the terms of the GNU
 * General Public License as published by the Free Software Foundation;
 * either version 3 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details. You should have received a
 * copy of the GNU General Public License along with this program; If
 * not, see http://www.gnu.org/licenses/.
 */

package org.ttrssreader.model;

import org.ttrssreader.controllers.Controller;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

abstract class MainCursorHelper {

    @SuppressWarnings("unused")
    private static final String TAG = MainCursorHelper.class.getSimpleName();

    protected int categoryId = Integer.MIN_VALUE;
    protected int feedId = Integer.MIN_VALUE;

    protected boolean selectArticlesForCategory;

    /**
     * Creates a new query
     */
    Cursor makeQuery(SQLiteDatabase db) {
        Cursor cursor;
        try {
            if (categoryId == 0 && (feedId == -1 || feedId == -2)) {

                // Starred/Published
                cursor = createCursor(db, true, false);

            } else {

                // normal query
                cursor = createCursor(db, false, false);

                // (categoryId == -2 || feedId >= 0): Normal feeds
                // (categoryId == 0 || feedId == Integer.MIN_VALUE): Uncategorized Feeds
                if ((categoryId == -2 || feedId >= 0) || (categoryId == 0 || feedId == Integer.MIN_VALUE)) {
                    if (Controller.getInstance().onlyUnread() && !checkUnread(cursor)) {

                        // Override unread if query was empty
                        cursor = createCursor(db, true, false);

                    }
                }
            }

        } catch (Exception e) {
            // Fail-safe-query
            cursor = createCursor(db, false, true);
        }
        return cursor;
    }

    /**
     * Tries to find out if the given cursor points to a dataset with unread articles in it, returns true if it does.
     *
     * @param cursor the cursor.
     * @return true if there are unread articles in the dataset, else false.
     */
    private static boolean checkUnread(Cursor cursor) {
        if (cursor == null || cursor.isClosed())
            return false; // Check null or closed

        if (!cursor.moveToFirst())
            return false; // Check empty

        do {
            if (cursor.getInt(cursor.getColumnIndex("unread")) > 0)
                return cursor.moveToFirst(); // One unread article found, move to first entry
        } while (cursor.moveToNext());

        cursor.moveToFirst();
        return false;
    }

    abstract Cursor createCursor(SQLiteDatabase db, boolean overrideDisplayUnread, boolean buildSafeQuery);

}
